Reactors in general and fluidized bed reactors in particular have been used to remove and recover phosphorous from wastewater that contains significant concentrations of phosphorus, often in the form of phosphate. Such wastewater may come from a wide range of sources. These include sources such as leaching from landfill sites, runoff from agricultural land, effluent from industrial processes, municipal wastewater, animal wastes, and the like. Such wastewater, if released into the environment without treatment, can result in excess effluent phosphorus levels.
Various phosphorus removal and recovery technologies exist. Some of the technologies provide fluidized bed reactors for removing phosphorus from aqueous solutions by producing struvite (MgNH4PO4 6H2O) or struvite analog or a phosphate compound in the form of pellets. Struvite can be formed by the reaction:Mg2++NH4++PO43−+6H2O↔MgNH4PO4.6H2O
Examples of reactors used to remove and recover phosphorus from wastewater solutions have been described in various references. They include the following:                Regy et al., Phosphate recovery by struvite precipitation in a stirred reactor, LAGEP (March to December 2001) includes a survey of various attempts to remove phosphorus and nitrogen from wastewater by struvite precipitation.        Trentelman, U.S. Pat. No. 4,389,317 and Piekema et al., Phosphate Recovery by the Crystallization Process: Experience and Developments, paper presented at the 2nd International Conference on Phosphate Recovery for Recycling from Sewage and Animal Wastes, Noordwijkerhout, the Netherlands, Mar. 12-13, 2001, disclose a reactor and method for precipitating phosphate in the form of calcium phosphate, magnesium phosphate, magnesium ammonium phosphate or potassium magnesium phosphate.        Ueno et al., Three years experience on operating and selling recovered struvite from full scale plant (2001), Environmental Technology, v. 22, p. 1373, discloses the use of sidestream crystallization reactors to remove phosphate in the form of magnesium ammonium phosphate (also known as struvite).        Tsunekawa et al., Patent Abstracts of Japan No. 11-267665 discloses a reactor for removing phosphorus from water.        Koch et al., Fluidized bed wastewater treatment, U.S. Pat. No. 7,622,047.        
Some problems that may occur in wastewater treatment and reactors include insufficient precipitation of solutes in treated wastewater and entrainment of precipitate particles in treated wastewater. There is a need for cost-effective methods and systems to address some or all of these problems.